Add functions to get user token key and secret
Added three functions to bring the user through the token retrieval process.
Also, updated the README to reflect these changes.

Each currently prints a URL for the user to navigate to, and instructions to
call the next function using the URL result. Ideally this should be more
automated, but this is a working solution in the meantime.
Move global variables out of low-level functions
Removed global variables from getSignature and getOauthFunctionUrl functions,
allowing them to be used without having defined these global variables. This
made it possible to remove workarounds in the user authentication functions,
which use a variety of token key/secret pairs.

This commit also also added a couple of global variables to pass data between
two user-called functions. Otherwise, the user would have to re-enter these
variables by hand. Once used, these temporary global variables are cleared.
Move user token retrieval to a separate page
Moved the user authentication and token retrieval to a separate HTML file,
which uses forms for user input. Previously, this system used the console
directly, which was significantly more awkward.

Removed user authentication functions from the tag script file.

Modified the README to reflect these changes.
Add submit button to file select
Added a submit button to the file select. The tag import process will not start
until this button is clicked, as opposed to the previous method, where tag
import started immediately upon closing the file select dialog.

Notably, this allows the same file to be submitted multiple times without
refreshing, although the value of the file selection does not change.
Hide second step of tagscript.html, increase text input width
Several minor appearance changes. The second step of the tag import script is
now hidden until the first step has been completed, as with userauth.html. In
addition, the text input for the API key and token key has a greater width, to
allow the user to see the entire keys at once.
Merge pull request #2 from gsolbeck/master

Add user token authentication through a 2nd web page, improve user interface (widen input fields, display sections only after previous sections are filled out and submitted)